Milling tool

ABSTRACT

A milling tool structure comprises a rotatable milling head which carries a cutting tool having a circular cutting edge. A power takeoff derived from rotation of the milling head is used to impart a relatively slower rotation to the cutting tool so as to present a continuously changing cutting point on its circular cutting edge to the work. The power takeoff can be in the form of a worm-type of drive or planetary-type of drive.

ilraited States Patent Vig 5] Feb. 15, 1972 [54] MILLING TOOL 2,530,50211/1950 Baney ..90/l1 [72] Inventor: lstvan vig, Zurich, Switzerland3,383,988 5/l968 Gruenlnger ..90/ll [73] Assignee: AktiengesellschaftBrown, Boveri 8: Cie, FOREGN PATENTS 0R APPLICATIONS Bade, swmflald686,819 1/1940 Germany ..90/11 .1

[22] Filed: July 15, 1969 Em G l d f 1 Primary miner-- i Wei en e d [21]App! 841500 Anorney-Pierce, Schefiler 8!. Parker [30] ForeignApplication Priority Data ABSTRACT Oct. 29, 1968 Switzerland ..l6097/68A milling tool Structure comprises a r t le milling head which carries acutting tool having a circular cutting edge. A [52] U5. Cl. ..90/11 A pw k ff eriv d fr m r ta i n of he milling head is use [51] Int. Cl..B23c 5/00 to impart a relatively slower rotation to the cutting toolso as [58] Field of Search ..90/ l 1.1, l 1, 15.2, 15 to present acontinuously changing cutting point on its circular cutting edge to thework. [56] References Cited The power takeoff can be in the form of aworm-type of drive UNITED STATES PATENTS or P yyp of drive- 2,l99,3795/1940 Tornebohn ..90/11 3 Claims, 7 Drawing Figures 6 i a s l l l s 7PATENTEDFEB 1 5 I972 SHEET 1 BF 3 INVENTOR B Isiuam Via A't'lzor 2.5.:

Fig 4b PAIENTEUFEB 15 1912 I 3.641 .871

SHEET 2 [IF 3 Fig 1c INVENTOR Isiuan V19 Y POJ iornzg PATENTEBFEB 1 5I972 SHEET 3 BF 3 Fig 2 Fig.3

Fig 4 MILLING TOOL This invention relates to the art of milling toolsand more particularly is directed to an improvement in the type ofmilling tool which is provided with a circular cutting edge.

A milling tool having a circular cutting edge has the advantage that thecutting edge extends over the entire circumference of the tool thusresulting in a longer tool life since freshly ground cutting points canbe made available simply by turning the tool slightly about its mountingaxis.

With the known types of construction for a circular edged milling tool,the tool is secured in place by means of a screw, and rotationaladjustment of the tool to present a fresh cutting point to the work isaccomplished by loosening the screw, making the desired rotaryadjustment and then retightening the screw. This is done with the toolat standstill. The disadvantage which attends such a construction isthat the milled surface is thus never quite uniform.

A cutting edge, which always comes into contact with the work at thesame point, wears out too soon. Particularly disad vantageous is thewear in broad finishing tools because the surface to be worked islimited, since the cutting edge cannot be exchanged during the millingoperation because of the resulting surface difference. With increasingwear at the cutting edge, small grooves are formed on the milled surfaceof the work which extend along the cutting arcs. The grooves have anadverse effect, for example, on a milled surface used for sealingpurposes, because they act like continuous channels.

In order to eliminate the disadvantages of the prior known constructionfor circular edged milling cutters, the present invention proposes thatthe milling cutter be so mounted on the milling head so as to bepositively rotated about its own axis as the milling head is rotated.The advantage of rotating the circular edged cutter about its own axisis that it results in a uniform wear of the edge throughout itscircumference and also in an equalization of the milled surface of thework.

In the following detailed description, two different embodiments of theinvention will be disclosed and these are illustrated in theaccompanying drawings wherein:

FIG. la is a view in top plan of the rotatable milling head with certainparts cut away to show the arrangement of a worm-type of drive by whichrotation is imparted to the circular edged milling tool as the millinghead is rotated;

FIG. 1b is a vertical diametral sectional view through the milling headshowing the tool element and its supporting spindle;

FIG. 1c is a side elevational view of the milling head with certainparts shown in section, the view being taken at a right angle to FIG.lb, to better illustrate the oblique character of the axis of the toolspindle relative to the rotational axis of the milling head;

FIG. 2 is a vertical diametral section similar to FIG. 1b illustrating asecond embodiment of the invention which utilizes a planetary-type ofgearing for imparting rotation to the circular edged tool by rotation ofthe milling head;

FIG. 3 is a detailed view of the tool element with the circular cuttingedge, this view being drawn to a larger scale for the sake of clarity;

FIG. 4 is a view showing the course of the milling grooves; and

FIG. 5 is another view of the tool element showing the detail of theclearance angle between the work and the edge of the tool.

With reference now to the drawings and to FIGS. la and lb, inparticular, the milling head of the milling machine is indicated bynumeral 1 and is mounted in the usual manner on a driving spindle l forrotation about its axis. The tool element 2 which has a frustoconicalconfiguration presenting a of cutting edge is secured within a recess ina spindle 3 which in turn is mounted for rotation about its axis bymeans of two axially spaced sets of ball bearings 4 and 6. The tool axisis coincident with the axis of rotation of its supporting spindle.Spindle 3 is provided with a thrust bearing 5 and a worm wheel 7intermediate the two ball bearing sets 4, 6 The worm wheel 7 mesheswith, and is driven by, a worm 8 secured upon a worm shaft 9 which ismounted for rotation about its axis within the body 0 the milling headby means of two sets of bearings ll, 12 located adjacent the oppositeends of this shaft. Secured upon the worm shaft 9 is a second worm wheel10 which meshes with, and is driven by, a second worm 13 which remainsstationary. Worm 13 is carried by a stationary hollow shaft 14 which issupported by a stationary part 15 of the milling machine, the hollowshaft 14 extending into an annular recess 1c located centrally withinthe body of the milling head such as to establish the axis of thestationary worm l3 coincident with the axis of rotation of the millinghead 1. While worm 13 remains stationary, it will be evident that arotary motion is nevertheless imparted to the wonn wheel 10 meshed withit as the milling head is rotated, thus carrying the worm wheel 10around the worm l3. Rotation of worm wheel I0 serves to drive the wormshaft 9 about its axis to thus impart a rotation to worm 8 which in turneffects rotation of its worm wheel 7 which in turn serves to rotatespindle 3 and thereby the circular edged tool 2. The drive arrangementis such that the tool rotates slowly in comparison to the rotationalspeed of the milling head and thus a slowly changing part of theperiphery of the cutting edge is presented to the work.

Due to the rotary movement of the cutting edge, a progressive or paringcut is produced which yields a better milled surface, and particularlyso in the case of softer work material. Moreover, since the cuttingpoint on the edge presented to the work is always being changed, wear onthe cutting edge will be distributed uniformly around its entireperiphery. This results in better cooling of the heated cutting zone sothat higher cutting velocities can be utilized. Also, rotary movement ofthe cutting edge has the effect that fine grooves formed on the milledsurface by increasing wear extend more or less transverse to the cuttingarcs, depending upon the speed of the cutting edge. By grinding surfaces2a around the periphery of the cutting edge, as shown in FIG. 3, it canbe achieved that the milled surface, similar to a scraped surface,exhibits minimum shell-like elevations, as shown in FIG. 4, which may bedesirable for certain functions to be served by the milled surface suchas for example surfaces which are utilized for sealing or for sliding.

The axis of the circular edged tool is arranged oblique to the axis ofrotation of the milling head 1 as shown more clearly in FIG. 5, hence ina tangential plane somewhat inclined with respect to the milling head.The oblique character of tool 2 is also shown in FIG. 10. In thismanner, a flat elliptical cutting edge with a clearance angle a1 isformed on the tool 2. This clearance angle can be increased to an angle112 by bevelling of the end face of the tool.

A second embodiment of the invention is illustrated in FIG. 2 whichemploys a planetary-type of drive for effecting slow rotation of thecircular edged tool as the milling head rotates.

In this embodiment, the rotary milling head is indicated by numeral 21,the circular edged tool element is again designed by numeral 2, and thespindle in which the cutter element is mounted has been designated 23.Spindle 23 is mounted for rotation in axially spaced bearings againillustrated by ball bearing sets 4 and 6, and the thrust bearing betweenthe two bearing sets is also again designated by 5, this bearing servingto absorb the axial pressure exerted on the spindle during the millingoperation. In order to provide a slow rotational drive for the spindle23 and hence also the tool element 2, a gearwheel 24 secured upon oneend of the spindle 23 meshes with one gear of a double-gearwheel 25which is mounted coaxially on the milling head 21 but is so arranged asto be freely rotatable on the head 21. The other gear of thedoublegearwheel 25 meshes with a planet gear 26 which also is in meshwith a ring gear 27 that is stationary and mounted on a stationary part15 of the milling machine.

Planet gear 26 turns on an axle 28 which is inserted in a disc 29fixedly secured on the rotary milling head 21.

Operation of the embodiment of FIG. 2 is as follows: When the millinghead 21 is driven in rotation, the disc 29 rotates and carries with itthe axle 28 so that axle 28 and planet gear 26 turn about the axis ofthe milling head 21. Due to the fact that planet gear 26 is meshed witha stationary ring gear 27, the planet gear 26 will also be driven aboutits own axis thus imparting rotation to the double-gearwheel 25 which inturn imparts rotation to gearwheel 24 and hence also to the spindle 23on which this gear is secured thus causing the spindle 23 and the toolelement 2 to rotate slowly about its axis in relation to the rotationalspeed of the milling head as a result of the reduction gearing effectproduced by the planetary drive.

l claim:

1. In a milling tool structure the combination comprising a millinghead, means mounting said milling head for driving rotation about itsaxis, a spindle, means mounting said spindle for rotation about its axisin the body of said milling head, the mounting axis of said spindlebeing displaced radially of and oblique to the mounting axis of saidmilling head, a cutting tool having a circular cutting edge secured toand coaxial with said spindle for engagement with the work as saidmilling head is rotated, and a power takeoff derived from rotation ofsaid milling head and which imparts a relatively slower rotation to saidspindle and cutting tool thereby to present a continuously changingcutting point on its circular cutting edge to the work.

2. A milling tool structure as defined in claim 1 wherein said powertakeoff for imparting rotation to said spindle and cutting tool isconstituted by a worm-type of drive which includes a wormshaft mountedfor rotation about its axis within the body of said milling head, a wormon said wormshaft meshed with and driving a worm wheel secured upon saidspindle, a second worm wheel secured upon said wormshaft, and astationary worm mounted concentrically with said milling head, saidsecond worm wheel being meshed with and rotatable about the axis of saidstationary worm as said milling head is rotated thereby to impartrotation to said second worm wheel and thence to said wormshaft andspindle.

3. A milling tool structure as defined in claim 1 wherein said powertakeoff for imparting rotation to said spindle and cutting tool isconstituted by a planetary-type of drive which includes a gearwheelsecured upon said spindle, a double gear wheel mounted coaxially on saidmilling head and which is freely rotatable relatively to said millinghead, said gearwheel on said spindle being meshed with one of the gearsof said double-gearwheel, the other gear of said double-gearwheel beingmeshed with a planet gear which is also meshed with a stationary ringgear mounted coaxially with said milling head, and said planet gearbeing mounted on an axle which is carried by said milling head in acircular path about the axis of said milling head as said milling headis rotated

1. In a milling tool structure the combination comprising a millinghead, means mounting said milling head for driving rotation about itsaxis, a spindle, means mounting said spindle for rotation about its axisin the body of said milling head, the mounting axis of said spindlebeing displaced radially of and oblique to the mounting axis of saidmilling head, a cutting tool having a circular cutting edge secured toand coaxial with said spindle for engagement with the work as saidmilling head is rotated, and a power takeoff derived from rotation ofsaid milling head and which imparts a relatively slower rotation to saidspindle and cutting tool thereby to present a continuously changingcutting point on its circular cutting edge to the work.
 2. A millingtool structure as defined in claim 1 wherein said power takeoff forimparting rotation to said spindle and cutting tool is constituted by aworm-type of drive which includes a wormshaft mounted for rotation aboutits axis within the body of said milling head, a worm on said wormshaftmeshed with and driving a worm wheel secured upon said spindle, a secondworm wheel secured upon said wormshaft, and a stationary worm mountedconcentrically with said milling head, said second worm wheel beingmeshed with and rotatable about the axis of said stationary worm as saidmilling head is rotated thereby to impart rotation to said second wormwheel and thence to said wormshaft and spindle.
 3. A milling toolstructure as defined in claim 1 wherein said power takeoff for impartingrotation to said spindle and cutting tool is constituted by aplanetary-type of drive which includes a gearwheel secured upon saidspindle, a double gear wheel mounted coaxially on said milling head andwhich is freely rotatable relatively to said milling head, saidgearwheel on said spindle being meshed with one of the gears Of saiddouble-gearwheel, the other gear of said double-gearwheel being meshedwith a planet gear which is also meshed with a stationary ring gearmounted coaxially with said milling head, and said planet gear beingmounted on an axle which is carried by said milling head in a circularpath about the axis of said milling head as said milling head isrotated.